This invention relates to novel couplers for use in hair coloring compositions comprising one or more oxidative hair coloring agents in combination with one or more oxidizing agents. The invention also relates to hair coloring compositions of these novel couplers and to coloring or dyeing of hair using compositions containing these couplers.
Coloration of hair is a procedure practiced from antiquity employing a variety of means. In modern times, the most extensively used method employed to color hair is to color hair by an oxidative dyeing process employing hair coloring systems utilizing one or more oxidative hair coloring agents in combination with one or more oxidizing agents.
Most commonly a peroxy oxidizing agent is used in combination with one or more oxidative hair coloring agents, generally small molecules capable of diffusing into hair and comprising one or more primary intermediates and one or more couplers. In this procedure, a peroxide material, such as hydrogen peroxide, is employed to activate the small molecules of primary intermediates so that they react with couplers to form larger sized compounds in the hair shaft to color the hair in a variety of shades and colors.
A wide variety of primary intermediates and couplers have been employed in such oxidative hair coloring systems and compositions. Among the primary intermediates employed there may be mentioned p-phenylenediamine, p-toluenediamine, p-aminophenol, 4-amino-3-methylphenol, and as couplers there may be mentioned resorcinol, 2-methylresorcinol, 3-aminophenol, and 5-amino-2-methylphenol. A majority of the shades have been produced with dyes based on p-phenylenediamine.
For providing a blue coloration to hair, m-phenylenediamine has been extensively used in combination with p-phenylenediamine as a primary intermediate. However, the blue dyes resulting undergo intramolecular cyclization to form red 2,8-diaminophenazine. This conversion has been suggested to be responsible for fading to red in hair (warm wearing or red fading). The rate of the cyclization depends upon positions of the substituents and can be decreased by the use of m-phenylenediamine with an electron-donating substituent such as an alkoxy group. Because of the color change over a period of time, there is a need for new blue couplers for use in oxidative hair dyeing compositions and systems.
This invention provides novel couplers of the formula (1): 
wherein R1 and R2 are each individually selected from hydrogen atoms, C1 to C5 alkyl, C1 to C5 mono or dihydroxyalkyl, phenyl or benzyl optionally substituted with a hydroxyl, amino or C1 to C3 alkoxy group, or R1 and R2 together with the nitrogen atom to which they are attached form a C3 to C6, preferably C4 to C6, saturated or unsaturated ring optionally containing in the ring one or more additional hetero atoms selected from O, S and N atoms.
These novel couplers are used to provide coloration to hair in which there is good dye uptake by the hair and provides shades or colors which are stable over a relatively long period of time. The novel couplers provide for dyeing of hair to impart color or shades that possess good wash fastness, good selectivity, perspiration resistance and do not undergo significant changes on exposure to light or shampooing.
Preferred coupler compounds of this invention are those of formula (1) 
wherein R1 and R2 are each individually selected from a hydrogen atom, a C1 to C3 alkyl group, preferably methyl groups; phenyl or benzyl optionally substituted with an alkoxy group, preferably a methoxy group, or R1 and R2 together with the nitrogen atom to which they are bound form a piperazine, piperidine, imidazole, or morpholine ring.
Especially preferred couplers of this invention are the following compounds:
1-(2,4-diamino-phenoxy)-3-(4-methoxy-phenylamino)-propan-2-ol;
1-(2,4-diamino-phenoxy)-3-piperidin-1-yl-propan-2-ol; and
1-(2,4-diamino-phenoxy)-3-methylamino)-propan-2-ol.
The novel coupler compounds of formula (1) of this invention are readily prepared according to the following reaction sequence where R1 and R2 are as defined herein before: 
In this synthesis a dinitrophenol (2) is reacted with an allyl halide and potassium carbonate in dimethylformamide (DMF) to produce the allyl ether compound (3). Epoxidation of the allyl ether (3) with m-chloroperbenzoic acid (MCPBA) in dichloromethane (DCM) produces the epoxide compound of formula (4) which upon treatment with a reagent of the formula NR1R2 results in the formation of compound of formula (5). Catalytic hydrogenation of the compound of formula (5) under hydrogen in the presence of Pd/C produces the coupler compounds of formula (1) of this invention. Alternatively, the dinitrophenol of formula (2) can be converted directly to the epoxide of formula (4) by reaction of the dinitrophenol with an epihalohydrin in the presence of potassium carbonate.